the parser chokes on a single dot

[szabgab]

In the PyDigger project I monitor PyPI and analyze recent releases. Among other things I use requirements-parser to parse the requirements.txt file.

Recently I encountered this project https://github.com/Te-k/pycrtsh where the "requirements.txt" file contains a single dot"

.

the parser raises an exception.

Is this a bug in requirements.parse or is having a single dot really incorrect?

See:

>>> import requirements
>>> for req in requirements.parse(".\n"): print(req)
... 

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/packaging/requirements.py", line 98, in __init__
    req = REQUIREMENT.parseString(requirement_string)
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 1654, in parseString
    raise exc
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 1644, in parseString
    loc, tokens = self._parse( instring, 0 )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 1402, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 3417, in parseImpl
    loc, exprtokens = e._parse( instring, loc, doActions )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 1402, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 3739, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 1402, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 3400, in parseImpl
    loc, resultlist = self.exprs[0]._parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 1406, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/pyparsing.py", line 2711, in parseImpl
    raise ParseException(instring, loc, self.errmsg, self)
pkg_resources._vendor.pyparsing.ParseException: Expected W:(abcd...) (at char 0), (line:1, col:1)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/requirements/parser.py", line 87, in parse
    yield Requirement.parse(line)
  File "/usr/local/lib/python3.9/site-packages/requirements/requirement.py", line 254, in parse
    return cls.parse_line(line)
  File "/usr/local/lib/python3.9/site-packages/requirements/requirement.py", line 232, in parse_line
    pkg_req = Req.parse(line)
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/__init__.py", line 3139, in parse
    req, = parse_requirements(s)
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/__init__.py", line 3084, in parse_requirements
    yield Requirement(line)
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/__init__.py", line 3094, in __init__
    super(Requirement, self).__init__(requirement_string)
  File "/usr/local/lib/python3.9/site-packages/pkg_resources/_vendor/packaging/requirements.py", line 100, in __init__
    raise InvalidRequirement(
pkg_resources.extern.packaging.requirements.InvalidRequirement: Parse error at "'.'": Expected W:(abcd...)